1. Field of the Invention
The present invention relates to a heat dissipating device, and particularly to a heat dissipating device with a fan holder guiding the airflow impelled by a fan.
2. Prior Art
Central processing unit (CPU) is the core administrator of electrical signals in most contemporary personal computers. Continued development of CPUs has enable them to perform more and more functions. Heat generated by CPUs has increased commensurately. Such heat can adversely affect the operational stability of computers. Measures must be taken to efficiently remove the heat from the CPU. Typically, a heat sink having great heat conductivity is mounted on the CPU to remove heat therefrom. A fan is often attached to the heat sink to provide forced air convection therefrom.
A conventional heat dissipation assembly as shown in FIG. 5 includes a fan 1 and a heat sink 3. The fan 1 defines four through holes 2 in four corners thereof. The heat sink 3 comprises a base 4, and a plurality of parallel fins 5 extending upwardly from the base 4. A plurality of screw threads 6 is formed in two outmost fins 5 at each side of the heat sink 3. Four screws 7 are received through the through holes 2 and engaged in the screw threads 6. However, the fins of the heat sink are normally relatively thin, and are prone to be deformed or damaged when the screws are engaged therewith. When this happens, the screws are easily loosened or even disengaged from the fins. When the fan is no longer securely mounted on the heat sink, the fan may operate less efficiently and cause noise.
A variety of fan holders have been developed for mounting a fan to a heat sink. One example is shown in FIG. 6. A fan holder 20 comprises a rectangular plate 26, four clasps 36 extending downwardly therefrom and four pins 28 extending upwardly therefrom. An opening 32 is defined in a middle of the plate 20 for providing airflow access from a fan 10 to a heat sink 40. The clasps 36 engage with hooks 48 of heat sink 40, thereby fastening the fan holder 20 to the heat sink 40. The pins 28 are received in through holes 12 of a frame of the fan 10. The fan is thereby securely mounted on top of the heat sink. However, the impeller 14 of the fan 10 dose not generate airflow. The part of the heat sink 40 under the impeller 14 of the fan 10 can not be blown by the fan 10. This significantly reduced the efficiency of the heat dissipation assembly.